Take a look at haxe[0] for a compile-to-js ML inspired language. It's relatively mature these days and integrates with existing typescript definitions via dts2hx[1]

I talk about this more here: https://news.ycombinator.com/item?id=26084187

[0] https://haxe.org/

[1] https://github.com/haxiomic/dts2hx